1. Field of the Invention
This invention relates to an improved process for the conversion of solids-containing liquid hydrocarbon oils, particularly solids-containing liquid hydrocarbon oils derived from coal, oil shale and tar sands. By "liquid hydrocarbon oils" we mean to include the organic liquid obtained from the physical and/or chemical treatment of coal, oil shale and tar sands. These "liquid hydrocarbon oils" can contain compounds of sulfur, oxygen nitrogen and other elements, as well as pure hydrocarbons.
Liquid hydrocarbon oils can contain solids that can interfere with subsequent processing thereof. These solids can be those which find their way into the liquid hydrocarbon oils during production thereof while in storage or during processing. Solids-containing liquid hydrocarbon oils that are preferably treated herein are solids-containing liquid hydrocarbon oils derived from coal, oil shale and tar sands.
These liquid hydrocarbon oils are old in the art and well-known and can be obtained in many ways. Reference, for example, for obtaining or producing these oils can be found in Kirk-Othmer Encyclopedia of Chemical Technology, Second Edition, 1969, John Wiley & Sons, Inc., New York, N.Y.: Volume 5, pages 606 to 678, for liquid hydrocarbon oils derived from coal; Volume 18, pages 1 to 20, for liquid hydrocarbon oils derived from oil shale; and Volume 19, pages 682 to 732, for liquid hydrocarbon oils derived from tar sands.
While these liquid hydrocarbon oils vary greatly in their composition, in the main they are composed of mono and polynuclear aromatic compounds, some of which can include chemically combined sulfur, nitrogen and/or oxygen. In general, their approximate composition, on a moisture-free, solids-free basis, can be as follows:
TABLE I ______________________________________ Weight Per Cent Broad Narrow Range Range ______________________________________ Carbon 80-95 83-92 Hydrogen 5-15 5-13 Nitrogen 0.1- 4 0.1- 3 Oxygen 0.1- 4 0.1-2.5 Sulfur 0.1-10 0.1- 5 ______________________________________
The solids that can be associated with the above-identified liquid hydrocarbon oils will contain in excess of about 50 weight percent of inorganic components, generally from about 60 to about 98 weight percent. Generally, these inorganic components will be, for example, iron compounds, such as iron pyrite; silica containing compounds, such as quartz, kaolin, mica, montmorillonite and zeolites; metal carbonates, such as calcite, dolomite and nahlcolite; etc. Based on the weight of the liquid hydrocarbon oil, the solids content thereof will be in the range of about 0.1 to about five weight percent, generally about 0.1 to about two weight percent.
The procedure defined herein can be used to improve the physical properties of the liquid hydrocarbon oil, for example, to reduce its specific gravity, pour point and/or viscosity and/or improve the chemical properties of the liquid hydrocarbon oil, for example, reduce its sulfur, oxygen and/or nitrogen content.
In order to upgrade (that is, improve the physical and/or chemical properties) liquid hydrocarbon oils, it is conventional to pass the same, together with hydrogen, through a catalyst-containing ebullating bed reactor or through a catalyst-containing fixed-bed reactor. With an ebullating bed, attrition rates in the reactor are high and catalyst losses are severe. When the liquid hydrocarbon oil being treated additionally contains solid materials, as herein, even poorer results are obtained because the presence of solid materials in the liquid hydrocarbon oils aggravates the attrition problems. Conventional fixed bed reactors work well when treating solids-free liquid hydrocarbon oils. However, when the liquid hydrocarbon oil being treated contains more than a few parts per million of solids, conventional fixed bed reactors quickly plug and become inoperable. Treating solids-containing liquid hydrocarbon oils in accordance with the process defined and claimed herein not only substantially reduces these attrition and plugging problems but, at the same time, results in the production of a liquid hydrocarbon oil having enhanced physical and/or chemical properties.
2. Description of the Prior Art
U.S. Pat. No. 2,985,582 to Oettinger discloses the removal of ash from crude oils, tars and their residues by heating said materials to a temperature of at least 250.degree. C. and then contacting the heated material with large-surfaced substances. In U.S. Pat. No. 3,575,847 Sprow et al. subject the liquid product from a coal liquefaction zone to hydrocracking in the presence of spherical hydrogenation catalysts.
The process of the invention, in general, comprises passing a solids-containing liquid hydrocarbon oil, together with hydrogen, into the reaction vessel referred to and described more fully hereinbelow. The reaction vessel contains a hydrogenation catalyst and is maintained under normal hydrogenating pressures and temperatures. After hydrogenation the solids that were present in the charge can be removed from the product stream. The balance of the product stream can thereafter be subjected to distillation to obtain products of various boiling ranges. Some of the products are useful per se as fuels. The remainder can be further treated by conventional petroleum processes including cracking, hydrocracking, hydrotreating and the like.
In accordance with the present invention, the solids-containing liquid hydrocarbon oil is contacted with hydrogen in the presence of a hydrogenation catalyst at a temperature between about 260.degree. to about 480.degree. C., preferably about 340.degree. to about 430.degree. C., at a pressure of about 500 to about 10,000 pounds per square inch gauge (about 35 to about 703 kilograms per square centimeter), preferably about 1000 to about 4000 pounds per square inch gauge (about 70 to about 281 kilograms per square centimeter), utilizing a weight hourly space velocity between about 0.25 to about 50 pounds of liquid hydrocarbon oil per pound of catalyst per hour (about 0.2 to about 50 kilograms of liquid hydrocarbon oil per kilogram of catalyst per hour), preferably about 1.0 to about 25 pounds of liquid hydrocarbon oil per pound of catalyst per hour (about 1.0 to about 25 kilograms of liquid hydrocarbon oil per kilogram of catalyst per hour), and added hydrogen in amounts between about 1000 to about 20,000 standard cubic feet per barrel of solid-containing liquid hydrocarbon oil (about 178 to about 3560 cubic meters per cubic meter of solids-containing liquid hydrocarbon oil) preferably between about 2000 to about 12,000 standard cubic feet per barrel of solids-containing liquid hydrocarbon oil (about 356 to about 2136 cubic meters per cubic meter of solids-containing liquid hydrocarbon oil). The exact conditions selected will depend on the catalyst, the particular charge stock to be treated, and the degree of physical and/or chemical conversion desired, etc. It is desirable to utilize as low a temperature as possible and still obtain the desired results. This is due to the fact that the rate of coke formation and the rate of catalyst deactivation becomes more pronounced at higher reaction temperatures. The hydrogen recycle rate does not vary significantly with various charge stocks and should be, for example, between about 1000 to about 15,000 standard cubic feet per barrel of solids-containing liquid hydrocarbon oil (about 178 to about 2670 cubic meters per cubic meter of solids-containing liquid hydrocarbon oil), preferably about 2000 to about 10,000 standard cubic feet per barrel of solids-containing liquid hydrocarbon oil (about 356 to about 1780 cubic meters per cubic meter of solids-containing liquid hydrocarbon oil).
Any catalytic component having hydrogenation activity, these being well-known to those having ordinary skill in the art, can be employed herein, but preferably the catalyst which is employed in the process of the invention comprises at least one hydrogenating component selected from the group consisting of the metals, metal sulfides and/or metal oxides of Groups VI and VIII of the Periodic Table. Particularly preferred among the hydrogenating metals are nickel, cobalt, molybdenum and tungsten. Particularly desirable catalysts comprise (a) a combination of about 2 to about 25 percent (preferably about 4 to about 16 percent) by weight molybdenum and at least one of the iron group metals where the iron group metals are present in such amounts that the atomic ratio of the iron group metals with respect to molybdenum is less than about 1.0 and (b) a combination of about 5 to about 40 percent (preferably about 10 to about 25 per cent) by weight of nickel and tungsten where the atomic ratio of tungsten to nickel is about 0.1:1 to about 5:1 (preferably about 0.3:1 to about 4:1), said hydrogenating component being composited with a porous support. These Group VI and Group VIII catalysts can employ promoters at levels not in excess of about eight percent, but preferably lower than about five percent. The best promoters are the elements of Groups II and IV. The most preferred ones are Ti, Zr, Sr, Mg, Zn and Sn. Catalysts of type "(a)" may contain molybdenum in the amounts conventionally used, i.e., about 2 to about 25 percent molybdenum based on the total weight of the catalyst including the porous carrier. Smaller amounts of molybdenum than about 2 percent may be used, but this reduces the activity. Larger amounts than about 25 percent can also be used but do not increase the activity and constitute an expense. The amounts of the iron group metals in "(a)" and "(b)" may be varied as long as the above proportions are used. However, in "(a)" we prefer to utilize two iron group metals, each in an atomic ratio to molybdenum between about 0.1 and about 0.2. All of the iron group metals may be present but we prefer to use only two. However, only one iron group element is employed when a group IVB promoter is used. The amount of the hydrogenating component based on the metal itself can suitable be from about 0.5 to about 40 percent by weight of the catalyst including the porous carrier, but is usually within the range of about 2 to about 30 percent by weight of the catalyst including the carrier.
When using a catalyst of type "(a)", we prefer to utilize one containing about 4 to about 16 percent by weight molybdenum, most preferably about 8 percent; about 0.2 to about 10 percent by weight nickel, most preferably about 0.5 percent; and about 0.5 to about 5 percent by weight cobalt, most preferably about 1.0 percent. When using a catalyst of type "(b)", we prefer to utilize one containing about 15 to about 25 percent (e.g., about 19 percent) tungsten and about 2 to about 10 percent (e.g., about 6 percent) nickel supported on a porous carrier, such as alumina.
The above-mentioned active hydrogenating components can also be present as mixtures. On the other hand, chemical combinations of the iron group metal oxides or sulfides with the Group VI oxide and/or sulfide can also be utilized. The catalytic hydrogenating components can be used with a variety of highly porous bases or supports which may or may not have catalytic activity of their own. Examples of such supports are alumina, bauxite, silica gel, kieselguhr, thoria, zirconia, molecular sieves or other zeolites, both natural and synthetic, or mixtures of the foregoing, as long as the particular catalyst support which is employed has pores sufficiently large to avoid quick plugging by the deposition of the ash and/or organo-metallic constituents of the solids-containing liquid hydrocarbon oil used as charge stock. By "highly porous" and "pores sufficiently large" is meant a pore volume of from about 0.1 to about 1.0 cc. per gram, preferably from about 0.25 to about 0.8 cc. per gram; a surface area from about 50 to about 450 m.sup.2 /gram, preferably from about 80 to about 300 m.sup.2 /gram; a pore radius size range (as measured with N.sub.2) from about 10 A to about 300 A with the average pore radius being from about 20 A to about 150 A. The catalyst will be more fully described hereinafter.
When treating a solids-containing liquid hydrocarbon oil according to the process of the invention, it is customary to continue the reaction until the catalyst activity has decreased markedly due to the deposition of ash and/or coke or other carbonaceous material thereon. In the process of the present invention the reaction will continue over an extended period of time before regeneration of the catalyst is required. When regeneration of the catalyst becomes necessary, the catalyst can be regenerated by combustion, i.e., by contact with an oxygen-containing gas such as air at an elevated temperature usually about 480.degree. C. or by any other means normally used to regenerate hydrogenation catalysts. The manner in which the catalyst is regenerated does not constitute a portion of the present invention.